The present invention relates to an ear plug for detecting bio-electrical signals. The invention relates more particularly to an ear plug for arrangement in an ear canal, where the ear plug comprises at least two electrodes prepared for detecting an EEG signal from a skin surface when the ear plug is arranged in the ear canal. The ear plug also comprises a housing with an outer wall made from a resilient material, and further comprises a signal acquisition circuit. The invention also relates to a method for manufacturing the ear plug.
Bio-electrical signals are here understood to be electrical potential differences across a tissue, organ or cell system or originating from the human body. The best known examples are Electrocardiogram (ECG) signals and Electroencephalogram (EEG) signals. An ear plug for detecting bio-electrical signals in the ear canal is made for arrangement fully or partly in the ear canal of a person. The ear plug is mainly designed for the detection of EEG signals.
EEG signals are electrical signals generated by a person's brain activity. In recent years, EEG monitoring systems, that may be carried or worn continuously by a person to be monitored, have been devised. A goal is to have personal wearable EEG monitors which can be carried without causing more inconvenience than glasses or a modern small hearing aid, even when carried over an extended interval of time, e.g. several months or years.
Such EEG monitors may be applied for purposes of surveillance of a condition of the person and for providing some kind of alarm or information in case predetermined conditions are met. The monitor may also be applied for collection of data for further analysis, e.g. for diagnostic purposes or for research use. An example of an application is for surveillance of persons having diabetes.
Measuring the EEG signal in the ear canal is known from WO 2011/000383 A1 disclosing an ear plug with EEG electrodes where the ear plug shape is individually matched to the users ear canal.
In WO 2013/026481 A1 it is described that the electrodes can be capacitive, i.e. being provided with a dielectric material on the surface intended to contact the skin surface.
WO 2007/047667 A2 discloses an ear plug made from a compressible material and provided with EEG electrodes.
One problem with the known solutions is that it is difficult to obtain an ear plug with EEG electrodes which is both pleasant and not annoying to wear for extended periods of time, and at the same time can obtain a stable and reliable EEG signal.